A soil anomaly detection system for detecting a place where a landslide disaster is likely to be caused is described, for example, in PTL1. The soil anomaly detection system described in PTL1, by use of an optical fiber sensor which is placed in the soil, measures a temperature and a quantity of strain at a position where the optical fiber sensor is placed, and detects an anomaly of the soil on the basis of the measured temperature and the measured quantity of the strain.
As a related art, a method for calculating a degree of collapse risk is disclosed in PTL 2, in which vibration is generated by a vibration generation source, and water content per volume of soil is estimated on the basis of a ratio of a longitudinal wave and a transversal wave of the vibration measured by a vibration sensor.